This invention relates to the art of nuclear reactor power plants. It has particular relationship to the refueling of the reactors of such plants. In carrying out the refueling, the reactor to be refueled is at the base of a pit in a containment filled with water to a depth of 20 or 30 feet. During refueling, component assemblies of the reactor or from refueling racks are engaged by grippers or grapples of a mast assembly, raised, transported from their position of origin and lowered in the position where they are to be deposited. The component assemblies are highly radioactive and are engaged, raised, transported and lowered under a substantial depth of water. To carry out this operation, there is provided apparatus including a bridge moveable along a track on the containment. A trolley is moveable on a track on the bridge. The trolley carries a mast assembly having a rotatable supporting mast from which the component-assembly engaging-raising-and-lowering means is suspended. This means is sometimes herein referred to as "component-assembly handling mechanism" or "assembly-handling mechanism" or simply "mechanism". With the bridge and trolley at selectably different positions along their tracks, the mast assembly is suspended with the assembly-handling mechanisms at selectably different positions of the area of the pit or of the reactor within the pit.
It is indispensable to successful refueling that the mechanism on the mast assembly be positioned during each operation to engage effectively and raise the exact assembly which is selected for transport. Since the reactor is under water, the positioning of the mechanisms and the engagement of the mechanisms with the component assemblies must be carried out with the necessary precision with at best a heavily clouded view of the nuclear core.
In accordance with the teachings of the prior art, index marks were provided on the trolley and bridge to locate the component assemblies to be moved in the reactor core. The index marks served to position the mast assembly over the theoretical location of a component assembly. If the assembly is out of position, difficult visual determinations were required to make the necessary adjustments. This operation was time consuming and required the utmost caution to preclude damage to the component assemblies.
It is the object of this invention to overcome the difficulties and drawbacks of the prior art. An object of this invention is to provide refueling apparatus for a reactor having facilities, whose calibration shall be maintained throughout a refueling operation, for reliably and precisely identifying the position of the mast assembly with reference to the reactor core. It is another object of this invention to provide refueling apparatus which shall not require a long festoon loop in the fluid and electric conductors between the trolley and the rotatable mast and in whose operations these conductors shall not be twisted. A third object of this invention is to provide refueling apparatus in whose operation rotation of the mast assembly shall not be restricted by the fluid and electric conductors and fouling of the hoist cables by these conductors on rotation of the mast assembly relative. The object of this invention is to provide refueling apparatus including position visual facilities for aligning the mast assembly with the component assembly to be transported for identifying and recording the location of component assemblies to be transferred and, if desirable, to provide a permanent record of the refueling and core mapping operation.
In accordance with this invention a television camera and a light source and reflector are mounted on the gripper housing of the mast assembly. The light source and reflector are positioned to illuminate a part of the top, i.e., the upper nozzle, in case of a fuel assembly to be transported or of another component assembly to be transported. The television camera is positioned to pick up an image of this part. The receiver connected to this television camera and the viewing monitor are in the control console. The viewing monitor may be provided with cross hairs which may serve to orient the mast assembly appropriately with reference to the fuel assembly. For example, the mast assembly may be rotated to a position in which the cross hairs pass through the centers of the images of the bolts in a corner of the fuel assembly which support the hold-down springs of the nozzle. The identification and location of the fuel assembly may be recorded in the computer. In addition, a video recorder may be provided. Such a recorder would produce a permanent record of the refueling and core mapping operations.